Synthesis of Ethanol from Biomass

ABSTRACT

A process for the selective production of ethanol by vapor phase reaction of acetic acid over a hydrogenating catalyst composition to form ethanol is disclosed and claimed. In an embodiment of this invention reaction of acetic acid and hydrogen over either cobalt and palladium supported on graphite or cobalt and platinum supported on silica selectively produces ethanol in a vapor phase at a temperature of about 250° C.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 13/056,470,which is a national stage of PCT/US2009/004197, filed on Jul. 20, 2009,which claims priority to U.S. patent application Ser. No. 12/221,239,filed Jul. 31, 2008, now U.S. Pat. No. 7,608,744, each of which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to a process for the productionof ethanol from acetic acid. More specifically, the present inventionrelates to a process including hydrogenating acetic acid utilizing acatalyst to form ethanol with high selectivity.

BACKGROUND

There is a long felt need for an economically viable process to convertacetic acid to ethanol. Ethanol is an important commodity feedstock fora variety of industrial products and is also used as a fuel additivewith gasoline. Ethanol can readily be dehydrated to ethylene, which canthen be converted to a variety of products, both polymeric and smallmolecule-based. Ethanol is conventionally produced from feedstocks whereprice fluctuations are becoming more significant. That is, fluctuatingnatural gas and crude oil prices contribute to fluctuations in the costof conventionally produced, petroleum, natural gas or corn or otheragricultural product-sourced ethanol, making the need for alternativesources of ethanol all the greater when oil prices and/or agriculturalproduct prices rise.

It has been reported that ethanol can be produced from the hydrogenationof acetic acid, but most of these processes feature several drawbacksfor a commercial operation. For instance, U.S. Pat. No. 2,607,807discloses that ethanol can be formed from acetic acid over a rutheniumcatalyst at extremely high pressures of 700-950 bars in order to achieveyields of around 88%, whereas low yields of only about 40% are obtainedat pressures of about 200 bar. Nevertheless, both of these conditionsare unacceptable and uneconomical for a commercial operation.

More recently, it has been reported that ethanol can be produced fromhydrogenating acetic acid using a cobalt catalyst again atsuperatmospheric pressures such as about 40 to 120 bar. See, forexample, U.S. Pat. No. 4,517,391 to Shuster et al. However, the onlyexample disclosed therein employs reaction pressure in the range ofabout 300 bar still making this process undesirable for a commercialoperation. In addition, the process calls for a catalyst containing noless than 50 percent cobalt by weight plus one or more members selectedfrom the group consisting of copper, manganese, molybdenum, chromium,and phosphoric acid, thus rendering the process economically non-viable.Although there is a disclosure of use of simple inert catalyst carriersto support the catalyst materials, there is no specific example ofsupported metal catalysts.

U.S. Pat. No. 5,149,680 to Kitson et al. describes a process for thecatalytic hydrogenation of carboxylic acids and their anhydrides toalcohols and/or esters utilizing a platinum group metal alloy catalysts.The catalyst is comprised of an alloy of at least one noble metal ofgroup VIII of the Periodic Table and at least one metal capable ofalloying with the group VIII noble metal, admixed with a componentcomprising at least one of the metals rhenium, tungsten or molybdenum.Although it has been claimed therein that improved selectivity toalcohols are achieved over the prior art references it was stillreported that 3 to 9 percent of alkanes, such as methane and ethane areformed as by-products during the hydrogenation of acetic acid to ethanolunder their optimal catalyst conditions.

U.S. Pat. No. 4,777,303 to Kitson et al. describes a process for theproductions of alcohols by the hydrogenation of carboxylic acids. Thecatalyst used in this case is a heterogeneous catalyst comprising afirst component which is either molybdenum or tungsten and a secondcomponent which is a noble metal of Group VIII of the Periodic Table ofthe elements, optionally on a support, for example, a high surface areagraphitized carbon. The selectivity to a combined mixture of alcohol andester is reported to be only in the range of about 73 to 87 percent withlow conversion of carboxylic acids at about 16 to 58 percent. Inaddition, no specific example of conversion of acetic acid to ethanol isprovided.

U.S. Pat. No. 4,804,791 to Kitson et al. describes another process forthe productions of alcohols by the hydrogenation of carboxylic acids. Inthis process, ethanol is produced from acetic acid or propanol isproduced from propionic acid by contacting either acetic acid orpropionic acid in the vapor phase with hydrogen at elevated temperatureand a pressure in the range from 1 to 150 bar in the presence of acatalyst comprising as essential components (i) a noble metal of GroupVIII of the Periodic Table of the elements, and (ii) rhenium, optionallyon a support, for example a high surface area graphitized carbon. Theconversion of acetic acid to ethanol ranged from 0.6% to 69% withselectivity to ethanol was in the range of about 6% to 97%.

From the foregoing it is apparent that existing processes do not havethe requisite selectivity to ethanol or existing art employs catalysts,which are expensive and/or non-selective for the formation of ethanoland produces undesirable by-products.

SUMMARY OF THE INVENTION

It has now been unexpectedly found that ethanol can be made on anindustrial scale directly from acetic acid with high selectivity andyield. More particularly, this invention provides a process for theselective formation of ethanol from acetic acid comprising:hydrogenating acetic acid over a suitable hydrogenating catalyst in thepresence of hydrogen. The catalyst suitable for the process of thisinvention is comprised of about 0.1 weight percent to about 20 weightpercent of cobalt supported on a suitable catalyst support incombination with one or more metal catalysts selected from the groupconsisting of palladium, platinum, rhodium, ruthenium, rhenium, iridium,chromium, copper, tin, molybdenum, tungsten, vanadium and zinc. Suitablecatalyst supports include without any limitation, silica, alumina,calcium silicate, silica-alumina, carbon, zirconia and titania.

DETAILED DESCRIPTION OF THE INVENTION

The invention is described in detail below with reference to numerousembodiments for purposes of exemplification and illustration only.Modifications to particular embodiments within the spirit and scope ofthe present invention, set forth in the appended claims, will be readilyapparent to those of skill in the art.

Unless more specifically defined below, terminology as used herein isgiven its ordinary meaning. Mole percent (mole % or %) and like termsrefer to mole percent unless otherwise indicated. Weight percent (wt %or %) and like terms refer to weight percent unless otherwise indicated.

“Conversion” is expressed as a mole percentage based on acetic acid inthe feed. The conversion of acetic acid (AcOH) is calculated from gaschromatography (GC) data using the following equation:

${{AcOH}\mspace{14mu} {conversion}\mspace{14mu} (\%)} = {100*\frac{{{mmol}\mspace{14mu} {AcOH}\mspace{14mu} {in}\mspace{14mu} ( {{feed}\mspace{14mu} {stream}} )} - {{mmol}\mspace{14mu} {AcOH}\mspace{14mu} {out}\mspace{14mu} ( {G\; C} )}}{{mmol}\mspace{14mu} {AcOH}\mspace{14mu} {in}\mspace{14mu} ( {{feed}\mspace{14mu} {stream}} )}}$

“Selectivity” is expressed as a mole percent based on converted aceticacid. For example, if the conversion is 50 mole % and 50 mole % of theconverted acetic acid is converted to ethanol, we refer to the ethanolselectivity as 50%. Selectivity to ethanol (EtOH) is calculated from gaschromatography (GC) data using the following equation:

${{Selectivity}\mspace{14mu} {to}\mspace{14mu} {EtOH}\mspace{14mu} (\%)} = {100*\frac{{mmol}\mspace{14mu} {EtOH}\mspace{14mu} {out}\mspace{14mu} ( {G\; C} )}{\frac{{Total}\mspace{14mu} {mmol}\mspace{14mu} C\mspace{14mu} {out}\mspace{14mu} ( {G\; C} )}{2} - {{mmol}\mspace{14mu} {AcOH}\mspace{14mu} {out}\mspace{14mu} ( {G\; C} )}}}$

Weight percent of a catalyst metal is based on metal weight and thetotal dry weight of metal and support.

The reaction proceeds in accordance with the following chemicalequation:

In accordance with the invention, conversion of acetic acid to ethanolcan be carried out in a variety of configurations, such as for examplein a single reaction zone which may be a layered fixed bed, if sodesired. An adiabatic reactor could be used, or a shell and tube reactorprovided with a heat transfer medium could be used. The fixed bed cancomprise a mixture of different catalyst particles or catalyst particleswhich include multiple catalysts as further described herein. The fixedbed may also include a layer of particulate material making up a mixingzone for the reactants. A reaction mixture including acetic acid,hydrogen and optionally an inert carrier gas is fed to the bed as astream under pressure to the mixing zone. The stream is subsequentlysupplied (by way of pressure drop) to the reaction zone or layer.Reaction zone comprises a catalytic composition including a suitablehydrogenating catalyst where acetic acid is hydrogenated to produceethanol. Any suitable particle size may be used depending upon the typeof reactor, throughput requirements and so forth.

Although various hydrogenating catalysts known to one skilled in the artcan be employed in hydrogenating acetic acid to form ethanol in theprocess of this invention it is preferred that a hydrogenating catalystemployed contains about 0.1 weight percent to about 20 weight percent ofcobalt on a suitable catalyst support. As noted earlier, it is furtherpreferred that the catalysts that are suitable in the process of thisinvention contain optionally a second and/or a third metal supported onthe same catalyst support. The following metals may be mentioned asthose metals suitable as a second and/or third metals without anylimitation: palladium, platinum, rhodium, ruthenium, rhenium, iridium,chromium, copper, tin, molybdenum, tungsten, vanadium, zinc and amixture thereof. Typically, it is preferred that cobalt in combinationwith at least one other metal on a suitable support can be used as ahydrogenating catalyst. Thus cobalt in combination with either palladiumor platinum are particularly preferred. Similarly, cobalt in combinationwith ruthenium, chromium or vanadium is also preferred. Examples ofmetals that can be used with cobalt as a third metal include without anylimitation any of the other metals listed above, such as for examplerhodium, iridium, copper, tin molybdenum and zinc.

Various catalyst supports known in the art can be used to support thecatalysts of this invention. Examples of such supports include withoutany limitation, zeolite, iron oxide, silica, alumina, titania, zirconia,silica-alumina, magnesium oxide, calcium silicate, carbon, graphite anda mixture thereof. Preferred supports are silica, alumina, calciumsilicate, carbon, zirconia and titania. More preferably silica is usedas a catalyst support in the process of this invention. It is alsoimportant to note that higher the purity of silica better it ispreferred as a support in this invention. Another preferred catalystsupport is calcium silicate.

In another embodiment of this invention the preferred catalyst supportis carbon. Various forms of carbon known in the art that are suitable ascatalyst support can be used in the process of this invention.Particularly preferred carbon support is a graphitized carbon,particularly the high surface area graphitized carbon as described inGreat Britain Patent No. 2,136,704. The carbon is preferably inparticulate form, for example, as pellets. The size of the carbonparticles will depend on the pressure drop acceptable in any givenreactor (which gives a minimum pellet size) and reactant diffusionconstraint within the pellet (which gives a maximum pellet size).

The carbon catalyst supports that are suitable in the process of thisinvention preferably porous carbon catalyst supports. With the preferredparticle sizes the carbon will need to be porous to meet the preferredsurface area characteristics.

The catalyst supports including the carbon catalyst supports may becharacterized by their BET, basal plane, and edge surface areas. The BETsurface area is the surface area determined by nitrogen adsorption usingthe method of Brunauer Emmett and Teller J. Am. Chem. Soc. 60,309(1938). The basal plane surface area is the surface area determined fromthe heat of adsorption on the carbon of n-dotriacontane from n-heptaneby the method described in Proc. Roy. Soc. A314 pages 473-498, withparticular reference to page 489. The edge surface area is the surfacearea determined from the heat of adsorption on the carbon of n-butanolfrom n-heptane as disclosed in the Proc. Roy. Soc. article mentionedabove with particular reference to page 495.

The preferred carbon catalyst supports for use in the present inventionhave a BET surface area of at least 100 m²/g, more preferably at least200 m²/ g, most preferably at least 300 m² /g. The BET surface area ispreferably not greater than 1000 m²/g, more preferably not greater than750 m²/g.

The preferred carbon support may be prepared by heat treating acarbon-containing starting material. The starting material may be anoleophillic graphite e.g. prepared as disclosed in Great Britain PatentNo. 1,168,785 or may be a carbon black.

However, oleophillic graphites contain carbon in the form of very fineparticles in flake form and are therefore not very suitable materialsfor use as catalyst supports. We prefer to avoid their use. Similarconsiderations apply to carbon blacks which also have a very fineparticle size.

The preferred materials are activated carbons derived from vegetablematerials e.g. coconut charcoal, or from peat or coal or fromcarbonizable polymers. The materials subjected to the heat treatmentpreferably have particle sizes not less than these indicated above asbeing preferred for the carbon support.

The preferred starting materials have the following characteristics: BETsurface area of at least 100, more preferably at least 500 m²/g.

The preferred heat treatment procedure for preparing carbon supportshaving the defined characteristics, comprise successively (1) heatingthe carbon in an inert atmosphere at a temperature of from 900° C. to3300° C., (2) oxidizing the carbon at a temperature between 300° C. and1200° C., (3) heating in an inert atmosphere at a temperature of between900° C. and 3000° C.

The oxidation step is preferably carried out at temperatures between300° and 600° C. when oxygen (e.g. as air) is used as the oxidizingagent.

The duration of the heating in inert gas is not critical. The timeneeded to heat the carbon to the required maximum temperature issufficient to produce the required changes in the carbon.

The oxidation step must clearly not be carried out under conditions suchthat the carbon combusts completely. It is preferably carried out usinga gaseous oxidizing agent fed at a controlled rate to avoid overoxidation. Examples of gaseous oxidizing agents are steam, carbondioxide, and gases containing molecular oxygen e.g. air. The oxidationis preferably carried out to give a carbon weight loss of at least 10weight percent based on weight of carbon subjected to the oxidationstep, more preferably at least 15 weight percent.

The weight loss is preferably not greater than 40 weight percent of thecarbon subjected to the oxidation step, more preferably not greater than25 weight percent of the carbon.

The rate of supply of oxidizing agent is preferably such that thedesired weight loss takes place over at least 2 hours, more preferablyat least 4 hours.

Where an inert atmosphere is required it may be supplied by nitrogen oran inert gas.

As noted above, the loading levels of cobalt on the catalyst support isgenerally in the range of about 0.1 weight percent to about 20 weightpercent. The amount of second or third metal loading on a support is notvery critical in this invention and can vary in the range of about 0.1weight percent to about 10 weight percent. A metal loading of about 1weight percent to about 6 weight percent based on the weight of thesupport is particularly preferred. Thus, for example 0.5 to 2 weightpercent of palladium supported on graphite which contains about 4 to 12weight percent of cobalt is particularly a preferred catalyst.Similarly, a catalyst containing about 0.5 to 2 weight percent ofplatinum supported on high purity silica which contains about 4 to 12weight percent of cobalt is also a preferred catalyst.

As already noted above, other metals that can preferably be used assecond metal with cobalt include ruthenium, chromium and vanadium. Ineach of these cases cobalt loading of 4 to 12 weight percent with secondmetal, i.e., ruthenium, chromium or vanadium loading of about 0.5 to 2weight percent are preferred. If a third metal is employed, its loadingcan also be in the range of about 0.5 weight percent to about 2 weightpercent, however, higher levels of metal loadings can also be useddepending upon the type of metal and the catalyst support used.

The metal impregnation can be carried out using any of the known methodsin the art. Typically, before impregnation the supports are dried at120° C. and shaped to particles having size distribution in the range ofabout 0.2 to 0.4 mm. Optionally the supports may be pressed, crushed andsieved to a desired size distribution. Any of the known methods to shapethe support materials into desired size distribution can be employed.

For supports having low surface area, such as for example alpha-alumina,the metal solutions are added in excess until complete wetness or excessliquid impregnation so as to obtain desirable metal loadings.

As noted above, the hydrogenation catalysts used in the process of thisinvention are at least bimetallic having cobalt as the main metal.Generally, without intending to be bound by any theory, it is believedthat one metal acts as a promoter metal and the other metal is the mainmetal. For instance, in the instant process of the invention, cobalt isconsidered to be main metal for preparing hydrogenation catalysts ofthis invention. The main metal can be combined with a promoter metalsuch as tungsten, vanadium, molybdenum, chromium or zinc. However, itshould be noted that sometimes main metal can also act as a promotermetal or vice versa. For example, nickel can be used as a promoter metalwhen iron is used as a main metal. Similarly, chromium can be used as amain metal in conjunction with copper (i.e., Cu—Cr as main bimetallicmetals), which can further be combined with promoter metals such ascerium, magnesium or zinc.

The bimetallic catalysts are generally impregnated in two steps. First,the “promoter” metal is added, followed by “main” metal. Eachimpregnation step is followed by drying and calcination. The bimetalliccatalysts may also be prepared by co-impregnation. In the case oftrimetallic Cu/Cr-containing catalysts as described above, a sequentialimpregnation may be used, starting with the addition of the “promoter”metal. The second impregnation step may involve co-impregnation of thetwo principal metals, i.e., Cu and Cr. For example, Cu—Cr—Co on SiO₂ maybe prepared by a first impregnation of chromium nitrate, followed by theco-impregnation of copper and cobalt nitrates. Again, each impregnationis followed by drying and calcinations. In most cases, the impregnationmay be carried out using metal nitrate solutions. However, various othersoluble salts which upon calcination releases metal ions can also beused. Examples of other suitable metal salts for impregnation includemetal hydroxide, metal oxide, metal acetate, ammonium metal oxide, suchas ammonium heptamolybdate hexahydrate, metal acids, such as perrhenicacid solution, metal oxalate, and the like.

Thus in one embodiment of this invention, there is provided ahydrogenation catalyst wherein the catalyst support is graphite with abimetallic loading of cobalt and palladium. In this aspect of theinvention, the loading of cobalt is about ten (10) weight percent andthe loading of palladium is about one (1) weight percent. A loadinglevel of cobalt at five (5) weight percent and loading level ofpalladium at 0.5 weight percent can also be employed if so desired.

In another embodiment of this invention, there is further provided ahydrogenation catalyst wherein the catalyst support is high puritysilica with a bimetallic loading of cobalt and platinum. In this aspectof the invention, the loading of cobalt is about ten (10) weight percentand the loading of platinum is about one (1) weight percent. Again inthis aspect of the invention, loading levels of cobalt at five (5)weight percent and loading levels of platinum at 0.5 weight percent canalso be employed.

In general, by the practice of this invention acetic acid canselectivity be converted to ethanol at very high rates. The selectivityto ethanol in general is very high and may be at least 40 percent. Underpreferred reaction conditions, acetic acid is selectively converted toethanol at a selectivity of about 60 percent or more preferably at aselectivity of at least 80 percent. Most preferably ethanol selectivityis at least 95 percent.

In another aspect of the process of this invention, the hydrogenation iscarried out at a pressure just sufficient to overcome the pressure dropacross the catalytic bed.

The reaction may be carried out in the vapor or liquid state under awide variety of conditions. Preferably, the reaction is carried out inthe vapor phase. Reaction temperatures may be employed, for example inthe range of about 200° C. to about 300° C., preferably about 225° C. toabout 275° C. The pressure is generally uncritical to the reaction andsubatmospheric, atmospheric or superatmospheric pressures may beemployed. In most cases, however, the pressure of the reaction will bein the range of about 1 to 30 atmospheres absolute, most preferably thepressure of reaction zone is in the range of about 10 to 25 atmospheresabsolute.

Although the reaction consumes two moles of hydrogen per mole of aceticacid to produce a mole of ethanol, the actual molar ratio of acetic acidto hydrogen in the feed stream may be varied between wide limits, e.g.from about 100:1 to 1:100. It is preferred however that such ratio be inthe range of about 1:20 to 1:2. More preferably the molar ratio ofacetic acid to hydrogen is about 1:5.

The raw materials used in connection with the process of this inventionmay be derived from any suitable source including natural gas,petroleum, coal, biomass and so forth. It is well known to produceacetic acid through methanol carbonylation, acetaldehyde oxidation,ethylene oxidation, oxidative fermentation, and anaerobic fermentationand so forth. As petroleum and natural gas have become more expensive,methods for producing acetic acid and intermediates such as methanol andcarbon monoxide from alternate carbon sources have drawn more interest.Of particular interest is the production of acetic acid from synthesisgas (syngas) that may be derived from any suitable carbon source. U.S.Pat. No. 6,232,352 to Vidalin, the disclosure of which is incorporatedherein by reference, for example, teaches a method of retrofitting amethanol plant for the manufacture of acetic acid. By retrofitting amethanol plant the large capital costs associated with CO generation fora new acetic acid plant are significantly reduced or largely eliminated.All or part of the syngas is diverted from the methanol synthesis loopand supplied to a separator unit to recover CO and hydrogen, which arethen used to produce acetic acid. In addition to acetic acid, theprocess can also be used to make hydrogen which is utilized inconnection with this invention.

U.S. Pat. No. RE 35,377 Steinberg et al., also incorporated herein byreference, provides a method for the production of methanol byconversion of carbonaceous materials such as oil, coal, natural gas andbiomass materials. The process includes hydrogasification of solidand/or liquid carbonaceous materials to obtain a process gas which issteam pyrolized with additional natural gas to form synthesis gas. Thesyngas is converted to methanol which may be carbonylated to aceticacid. The method likewise produces hydrogen which may be used inconnection with this invention as noted above. See also, U.S. Pat. No.5,821,111 Grady et al., which discloses a process for converting wastebiomass through gasification into synthesis gas as well as U.S. Pat. No.6,685,754 Kindig et al., the disclosures of which are incorporatedherein by reference.

The acetic acid may be vaporized at the reaction temperature, and thenit can be fed along with hydrogen in undiluted state or diluted with arelatively inert carrier gas, such as nitrogen, argon, helium, carbondioxide and the like.

Alternatively, acetic acid in vapor form may be taken directly as crudeproduct from the flash vessel of a methanol carbonylation unit of theclass described in U.S. Pat. No. 6,657,078 of Scates et al., thedisclosure of which is incorporated herein by reference. The crude vaporproduct may be fed directly to the reaction zones of the presentinvention without the need for condensing the acetic acid and light endsor removing water, saving overall processing costs.

Contact or residence time can also vary widely, depending upon suchvariables as amount of acetic acid, catalyst, reactor, temperature andpressure. Typical contact times range from a fraction of a second tomore than several hours when a catalyst system other than a fixed bed isused, with preferred contact times, at least for vapor phase reactions,between about 0.5 and 100 seconds.

Typically, the catalyst is employed in a fixed bed reactor e.g. in theshape of an elongated pipe or tube where the reactants, typically in thevapor form, are passed over or through the catalyst. Other reactors,such as fluid or ebullient bed reactors, can be employed, if desired. Insome instances, it is advantageous to use the hydrogenation catalysts inconjunction with an inert material to regulate the pressure drop, flow,heat balance or other process parameters in the catalyst bed includingthe contact time of the reactant compounds with the catalyst particles.

In one of the preferred embodiments there is also provided a process forselective and direct formation of ethanol from acetic acid comprising:contacting a feed stream containing acetic acid and hydrogen at anelevated temperature with a suitable hydrogenating catalyst containingabout 1 weight percent to about 15 weight percent of cobalt on asuitable catalyst support and a second metal supported on said supportand wherein said second metal is selected from the group consisting ofpalladium, platinum, copper, tin, molybdenum and tungsten.

In this embodiment of the process of this invention, the preferredhydrogenation catalyst contains one (1) weight percent palladium orplatinum with about ten (10) weight percent cobalt. In this embodimentof the process of this invention it is preferred that the hydrogenationcatalysts is layered in a fixed bed and the reaction is carried out inthe vapor phase using a feed stream of acetic acid and hydrogen in themolar range of about 1:20 to 1:2 and at a temperature in the range ofabout 225° C. to 275° C. and at a pressure of reaction zones in therange of about 10 to 25 atmospheres absolute, and the contact time ofreactants is in the range of about 0.5 and 100 seconds.

The following examples describe the procedures used for the preparationof various catalysts employed in the process of this invention.

Example A

Preparation of 10 Weight Percent cobalt and 1 Weight Percent Palladiumon Graphite

Powdered and meshed graphite (100 g) of uniform particle sizedistribution of about 0.2 mm was dried at 120° C. in an oven undernitrogen atmosphere overnight and then cooled to room temperature. Tothis was added a solution of palladium nitrate (Heraeus) (2.2 g) indistilled water (22 ml). The resulting slurry was dried in an ovengradually heated to 110° C. (>2 hours, 10° C./min.). The impregnatedcatalyst mixture was then calcined at 500° C. (6 hours, 1° C./min). Tothis calcined and cooled material was added a solution of cobalt nitratehexahydrate (49.4 g) in distilled water (50 ml). The resulting slurrywas dried in an oven gradually heated to 110° C. (>2 hours, 10°C./min.). The impregnated catalyst mixture was then calcined at 500° C.(6 hours, 1° C./min).

Example B Preparation of 5 Weight Percent Cobalt and 0.5 Weight PercentPalladium on Graphite

Powdered and meshed graphite (100 g) of uniform particle sizedistribution of about 0.2 mm was dried at 120° C. in an oven undernitrogen atmosphere overnight and then cooled to room temperature. Tothis was added a solution of palladium nitrate (Heraeus) (1.1 g) indistilled water (11 ml). The resulting slurry was dried in an ovengradually heated to 110° C. (>2 hours, 10° C./min.). The impregnatedcatalyst mixture was then calcined at 500° C. (6 hours, 1° C./min). Tothis calcined and cooled material was added a solution of cobalt nitratehexahydrate (24.7 g) in distilled water (25 ml). The resulting slurrywas dried in an oven gradually heated to 110° C. (>2 hours, 10°C./min.). The impregnated catalyst mixture was then calcined at 500° C.(6 hours, 1° C./min).

Example C Preparation of 10 Weight Percent Cobalt and 1 Weight PercentPlatinum on High Purity Silica

Powdered and meshed high purity silica (100 g) of uniform particle sizedistribution of about 0.2 mm was dried at 120° C. in an oven undernitrogen atmosphere overnight and then cooled to room temperature. Tothis was added a solution of platinum nitrate (Chempur) (1.64 g) indistilled water (16 ml). The resulting slurry was dried in an ovengradually heated to 110° C. (>2 hours, 10° C./min.). The impregnatedcatalyst mixture was then calcined at 500° C. (6 hours, 1° C./min). Tothis calcined and cooled material was added a solution of cobalt nitratehexahydrate (49.4 g) in distilled water (50 ml). The resulting slurrywas dried in an oven gradually heated to 110° C. (>2 hours, 10°C./min.). The impregnated catalyst mixture was then calcined at 500° C.(6 hours, 1° C./min).

Example D Preparation of 10 Weight Percent Cobalt and 1 Weight PercentPlatinum on Calcium Silicate

Powdered and meshed calcium silicate (100 g) of uniform particle sizedistribution of about 0.2 mm was dried at 120° C. in an oven undernitrogen atmosphere overnight and then cooled to room temperature. Tothis was added a solution of platinum nitrate (Chempur) (1.64 g) indistilled water (16 ml). The resulting slurry was dried in an ovengradually heated to 110° C. (>2 hours, 10° C./min.). The impregnatedcatalyst mixture was then calcined at 500° C. (6 hours, 1° C./min). Tothis calcined and cooled material was added a solution of cobalt nitratehexahydrate (49.4 g) in distilled water (50 ml). The resulting slurrywas dried in an oven gradually heated to 110° C. (>2 hours, 10°C./min.). The impregnated catalyst mixture was then calcined at 500° C.(6 hours, 1° C./min).

Example E Preparation of 10 Weight Percent Cobalt and 1 Weight PercentChromium on Graphite

Powdered and meshed graphite (100 g) of uniform particle sizedistribution of about 0.2 mm was dried at 120° C. in an oven undernitrogen atmosphere overnight and then cooled to room temperature. Tothis was added a solution of chromium nitrate nonahydrate (Alfa Aesar)(6.5 g) in distilled water (13 ml). The resulting slurry was dried in anoven gradually heated to 110° C. (>2 hours, 10° C./min.). Theimpregnated catalyst mixture was then calcined at 500° C. (6 hours, 1°C./min). To this calcined and cooled material was added a solution ofcobalt nitrate hexahydrate (49.4 g) in distilled water (50 ml). Theresulting slurry was dried in an oven gradually heated to 110° C. (>2hours, 10° C./min.). The impregnated catalyst mixture was then calcinedat 500° C. (6 hours, 1° C./min). Gas Chromatographic (GC) analysis ofthe Products

The analysis of the products was carried out by online GC. A threechannel compact GC equipped with one flame ionization detector (FID) and2 thermal conducting detectors (TCDs) was used to analyze the reactantsand products. The front channel was equipped with an FID and a CP-Sil 5(20 m)+WaxFFap (5 m) column and was used to quantify:

Acetaldehyde

Ethanol

Acetone

Methyl acetate

Vinyl acetate

Ethyl acetate

Acetic acid

Ethylene glycol diacetate

Ethylene glycol

Ethylidene diacetate

Paraldehyde

The middle channel was equipped with a TCD and Porabond Q column and wasused to quantify:

CO₂

Ethylene

Ethane

The back channel was equipped with a TCD and Molsieve 5A column and wasused to quantify:

Helium

Hydrogen

Nitrogen

Methane

Carbon monoxide

Prior to reactions, the retention time of the different components wasdetermined by spiking with individual compounds and the GCs werecalibrated either with a calibration gas of known composition or withliquid solutions of known compositions. This allowed the determinationof the response factors for the various components.

Example 1

The catalyst utilized was 10 weight percent cobalt and 1 weight percentpalladium on Graphite prepared in accordance with the procedure ofExample A

In a tubular reactor made of stainless steel, having an internaldiameter of 30 mm and capable of being raised to a controlledtemperature, there are arranged 50 ml of 10 weight percent cobalt and 1weight percent palladium on Graphite. The length of the catalyst bedafter charging was approximately about 70 mm.

A feed liquid was comprised essentially of acetic acid. The reactionfeed liquid was evaporated and charged to the reactor along withhydrogen and helium as a carrier gas with an average combined gas hourlyspace velocity (GHSV) of about 2500 hr⁻¹ at a temperature of about 250°C. and pressure of 22 bar. The resulting feed stream contained a molepercent of acetic acid from about 4.4% to about 13.8% and the molepercent of hydrogen from about 14% to about 77%. A portion of the vaporeffluent was passed through a gas chromatograph for analysis of thecontents of the effluents. The selectivity to ethanol was 97.5% at aconversion of acetic acid of 18.5%.

Example 2

The catalyst utilized was 5 weight percent cobalt and 0.5 weight percentplatinum on graphite prepared in accordance with the procedure ofExample B.

The procedure as set forth in Example 1 is substantially repeated withan average combined gas hourly space velocity (GHSV) of 2,500 hr⁻¹ ofthe feed stream of the vaporized acetic acid and hydrogen at atemperature of 225° C. and pressure of 22 bar. A portion of the vaporeffluent is passed through a gas chromatograph for analysis of thecontents of the effluents. The acetic acid conversion is 20% and ethanolselectivity is 95%.

Example 3

The catalyst utilized was 10 weight percent cobalt and 1 weight percentplatinum on High Purity Silica prepared in accordance with the procedureof Example C.

The procedure as set forth in Example 1 was substantially repeated withan average combined gas hourly space velocity (GHSV) of 2,500 hr⁻¹ ofthe feed stream of the vaporized acetic acid and hydrogen at atemperature of 250° C. and pressure of 22 bar. A portion of the vaporeffluent was passed through a gas chromatograph for analysis of thecontents of the effluents. The acetic acid conversion was 71% andethanol selectivity was 96%.

Example 4

The catalyst utilized was 10 weight percent cobalt and 1 weight percentplatinum on calcium silicate prepared in accordance with the procedureof Example D.

The procedure as set forth in Example 1 was substantially repeated withan average combined gas hourly space velocity (GHSV) of 2,500 hr⁻¹ ofthe feed stream of the vaporized acetic acid and hydrogen at atemperature of 250° C. and pressure of 22 bar. A portion of the vaporeffluent was passed through a gas chromatograph for analysis of thecontents of the effluents. The acetic acid conversion was 50% andethanol selectivity was 94%.

Example 5

The catalyst utilized was 10 weight percent cobalt and 1 weight percentchromium on graphite prepared in accordance with the procedure ofExample E.

The procedure as set forth in Example 1 is substantially repeated withan average combined gas hourly space velocity (GHSV) of 2,500 hr⁻¹ ofthe feed stream of the vaporized acetic acid and hydrogen at atemperature of 250° C. and pressure of 22 bar. A portion of the vaporeffluent was passed through a gas chromatograph for analysis of thecontents of the effluents. The acetic acid conversion is 38% and ethanolselectivity is 96%.

While the invention has been illustrated in connection with particularexamples, modifications to these examples within the spirit and scope ofthe invention will be readily apparent to those of skill in the art. Inview of the foregoing discussion, relevant knowledge in the art andreferences discussed above in connection with the Background andDetailed Description, the disclosures of which are all incorporatedherein by reference, further description is deemed unnecessary.

1. A method for producing ethanol from biomass, said method comprising:(i) converting said biomass into a first stream comprising syngas; (ii)catalytically converting at least some of said syngas into a secondstream comprising methanol; (iii) separating some of said syngas intohydrogen and carbon monoxide; (iv) catalytically converting at leastsome of said methanol with some of said carbon monoxide into a thirdstream comprising acetic acid; and (v) reducing at least some of saidacetic acid with some of said hydrogen into a fourth stream comprisingethanol.
 2. The process according to claim 1, wherein step (i) includeshydrogasification of solid and/or liquid carbonaceous materials toobtain a process gas which is steam pyrolized to form the syngas.
 3. Theprocess according to claim 1, wherein the reducing occurs in thepresence of a catalyst comprising cobalt.
 4. The process according toclaim 3, wherein the reducing occurs in the presence of a catalystcomprising molybdenum.
 5. The process according to claim 1, wherein thereducing occurs in the presence of a catalyst comprising cobalt and asecond metal on a catalyst support, wherein the cobalt is present in anamount from 0.1 weight percent to 20 weight percent, and wherein thesecond metal is selected from the group consisting of palladium,platinum, and chromium.
 6. The process according to claim 5, wherein thecatalyst support is selected from the group consisting of silica,alumina, calcium silicate, carbon, zirconia and titania.
 7. The processaccording to claim 5, wherein the second metal is palladium.
 8. Theprocess according to claim 7, wherein the loading of cobalt is from 4 to12 weight percent and the loading of palladium is from 0.5 to 2 weightpercent and the catalyst support is graphite.
 9. The process accordingto claim 5, wherein the second metal is platinum.
 10. The processaccording to claim 9, wherein cobalt loading is from 4 to 12 weightpercent and platinum loading is from 0.5 to 2 weight percent and thecatalyst support is high purity silica.
 11. The process according toclaim 5, wherein selectivity to ethanol based on acetic acid consumed isat least 40 percent.
 12. The process according to claim 5, whereinselectivity to ethanol based on acetic acid consumed is at least 60percent.
 13. The process according to claim 5, wherein selectivity toethanol based on acetic acid consumed is at least 80 percent.
 14. Theprocess according to claim 5, wherein selectivity to ethanol based onacetic acid consumed is at least 95 percent.
 15. The process accordingto claim 5, wherein the reducing is carried out at a temperature in therange of 225° to 275° C.
 16. The process according to claim 5, whereinthe cobalt is present in an amount from 1 weight percent to 15 weightpercent.
 17. A method for producing ethanol from biomass, said methodcomprising: (i) converting said biomass into syngas; (ii) reacting thesyngas in the presence of a catalyst to form methanol; (iii) supplyingpart of the syngas to a separator unit to recover carbon monoxide andhydrogen; (iv) carbonylating the methanol with the carbon monoxide toform acetic acid; and (v) reducing at least some of the acetic acid withthe hydrogen to form the ethanol.
 18. The process according to claim 17,wherein step (i) includes hydrogasification of solid and/or liquidcarbonaceous materials to obtain a process gas which is steam pyrolizedto form the syngas.
 19. The process according to claim 17, wherein thereducing occurs in the presence of a catalyst comprising cobalt.
 20. Theprocess according to claim 19, wherein the reducing occurs in thepresence of a catalyst comprising molybdenum.
 21. The process accordingto claim 17, wherein the reducing occurs in the presence of a catalystcomprising cobalt and a second metal on a catalyst support, wherein thecobalt is present in an amount from 0.1 weight percent to 20 weightpercent, and wherein the second metal is selected from the groupconsisting of palladium, platinum, and chromium.
 22. The processaccording to claim 21, wherein the catalyst support is selected from thegroup consisting of silica, alumina, calcium silicate, carbon, zirconiaand titania.
 23. The process according to claim 21, wherein the secondmetal is palladium.
 24. The process according to claim 23, wherein theloading of cobalt is from 4 to 12 weight percent and the loading ofpalladium is from 0.5 to 2 weight percent and the catalyst support isgraphite.
 25. The process according to claim 21, wherein the secondmetal is platinum.
 26. The process according to claim 25, wherein cobaltloading is from 4 to 12 weight percent and platinum loading is from 0.5to 2 weight percent and the catalyst support is high purity silica. 27.The process according to claim 21, wherein selectivity to ethanol basedon acetic acid consumed is at least 40 percent.
 28. The processaccording to claim 21, wherein selectivity to ethanol based on aceticacid consumed is at least 60 percent.
 29. The process according to claim21, wherein selectivity to ethanol based on acetic acid consumed is atleast 80 percent.
 30. The process according to claim 21, whereinselectivity to ethanol based on acetic acid consumed is at least 95percent.
 31. The process according to claim 21, wherein the reducing iscarried out at a temperature in the range of 225° to 275° C.
 32. Theprocess according to claim 21, wherein the cobalt is present in anamount from 1 weight percent to 15 weight percent.